1. Field of the Invention
The present invention relates to a shift device for an inline transmission, with:                a shift shaft which is rotated during selection movements and is offset axially during shift movements;        a plurality of shift members which each are mounted movably or pivotably in the axial direction, for the actuation at least one assigned shift clutch;        a plurality of shift fingers which are secured to the shift shaft and each extend towards one side, each shift finger being assigned to one of the shift members and being arranged in such a way that, in a defined rotary selection position of the shift shaft, the shift finger is coupled axially to its assigned shift member, in order to drive the shift member during an axial movement of the shift shaft; and        a blocking device for preventing two or more gears of the transmission from being shifted simultaneously, the blocking device having a plurality of individual blocking elements mounted fixedly with respect to the casing.        
2. Description of the Related Art
A shift device of this type is known from DE 43 42 957 A1.
The invention relates, in general terms, to a shift device for the actuation a manual shift transmission of the in-line form of construction. (including in-line transaxle), with a device for preventing a situation where a plurality of gears can be shifted simultaneously, and with latching for the individual shift rockers/forks.
In the field of shift devices for transmissions, in particular of transmission for motor vehicles, the individual shift members (shift forks or shift rockers) are often actuated by means of a plurality of shift rods. This is known, for example, from DE 29 35 590 C2.
It is known, as a blocking device for the plurality of shift rods, to move a blocking slide transversely to the extent of the shift rods (DE 37 30 230 C1).
DE 199 51 683 A1 discloses a shift device for a motor vehicle transmission, in which a central shift shaft has provided on it a plurality of shift fingers which can be positively coupled axially to respective shift members.
A blocking plate which is arranged parallel to the shift shaft and overall is mounted so as to be displaceable in a direction transverse to the shift shaft, serves as a blocking device. For this purpose, the blocking plate is connected to a coupling lever which is secured fixedly in terms of rotation to the shift shaft. The shift members have provided on them respective blocking elements which, in a blocking position, engage into respective grooves of the blocking plate. When a shift member is selected as a result of the rotational movement of the shift shaft, the blocking plate releases the blocking element of the shift member, so that the shift member can be displaced axially or pivoted. In that rotary position of the shift shaft, the blocking elements of the other shift members each engage into an assigned groove of the blocking plate and are consequently fixed axially, so that shifting-in the assigned gears is prevented.
Disadvantages of this prior art are the complicated coupling between shift shaft and blocking plate and the complicated mounting of the blocking plate.
Two embodiments of blocking devices are known from DE 43 42 957 A1 mentioned in the introduction.
In one embodiment of this prior art, individual blocking elements in the form of blocking beans are mounted on the shift members. In a blocking state, the blocking members are pressed into recesses in the transmission casing, counter to spring prestress, by means of respective coupling members on the shift shaft. Insofar as one shift member is selected, the assigned coupling member is brought into a rotary position such that the blocking element can penetrate into a recess of the coupling member by means of the spring prestress, in order thereby to release the positive coupling between transmission casing and shift member.
In a second embodiment of this prior art, a plurality of individual blocking elements are mounted on the transmission casing and are prestressed elastically in a direction towards the shift shaft. Each of the shift members is assigned a coupling member on the shift shaft. The coupling member has, on the one hand, a shift finger for engaging to a shift fork of the respective shift member. On the opposite side, the coupling elements each have an axial groove and a depression emanating from the axial groove. In a blocking state, the blocking elements each engage into the depressions and thus fix the coupling elements. As a result of the rotation of the shift shaft, assigned driving parts on the shift shaft press the blocking element to be released out of the depression, so that the blocking element is freely movable in the axial groove. At the same time, the driving part drives the selected coupling element during an axial movement, so that the shift member assigned to the coupling element is driven axially by the shift shaft.
In both embodiments, the coupling elements are complicated to produce and the transmission casing has to be prepared specially for the mounting of the blocking elements.
DE 199 01 056 A1 discloses a shift system similar to the second embodiment of DE 43 42 957 A1. In contrast to this, the axial grooves of the coupling elements are provided with latching depressions, so that the blocking elements not only serve for blocking, but also for latching in the respective shift positions.
Overall, the prior art, in each case, has at least one of the following disadvantages:                A complicated mechanism for blocking;        Friction between shift element and blocking element, in addition to the friction of the latching;        The necessity to link together a positive connection with the shift rockers/forks into one plane;        Casing bores for blocking elements;        Casing bores for latching elements;        Additional blocking/latching contours on the shift rockers/forks necessary;        Depending on the system, blocking can take place only during the shift or selection movement;        Gears which have been selected as a result of the action of external forces (for example, during transport) and are not selected by the shift shaft can no longer be shifted out.        